JPS6042831B2 - Composition for electrocoating aluminum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for electrocoating aluminum or aluminum alloys.

Conventionally, a conductive object is immersed in a water-soluble or water-dispersible paint, and a voltage is applied between the object and an electrode installed in isolation in the paint, thereby passing an electric current through the object. An electrodeposition method in which a water-insoluble coating base material is deposited in the vicinity and adsorbed onto the surface of the object for coating is disclosed in Japanese Patent Publication No. 47-8.
It is well known that this method is clearly known from No. 7 (2) and others, and is currently widely used industrially.

Furthermore, there is an alumite processing method in which immediately after anodizing aluminum or aluminum alloy, a thermosetting water-soluble paint or water-based emulsion is electrodeposited particularly inside the micropores existing in the oxide film, and then heated and hardened. Special Publication No. 41-14967 (Patent No. 517521)
No.). However, generally aluminum or aluminum alloy (hereinafter simply "aluminum")
It is called.

) The size of the micropores present in the anodic oxide film is 100
~500Λ, and by electrodeposition coating within such micropores,
In order to deposit a water-soluble paint or an aqueous emulsion, the resin must enter the pores, and in the case of emulsions it naturally has a very limited particle size, i.e. at least a particle size smaller than the pores. It is obvious that it must be an emulsion. Furthermore, since the pores have just been anodized, water is naturally contained in the pores, and it is well known that sulfuric acid alumite, which is the most commonly used industrially, contains acidic water containing sulfuric acid. Although it has been explained that water and resin replace each other, the resin that is supposed to replace water is hydrophobic and repels water not only in the electrodeposited state but also in acidic water. is well known and therefore cannot replace the water in the pores. That is, it is obvious that the resin is repelled by the water in the pores and cannot enter. Therefore, this method of electrodepositing the resin into the pores of the alumite layer immediately after anodization probably involves the use of a water-soluble paint or water-based emulsion with special properties. Furthermore, it is common knowledge that in order to maintain sufficient durability of the anodic oxide film, it is necessary to carry out sufficient sealing treatment, but Japanese Patent Publication No. 14967/1973 states that sealing should never be carried out. This method is completely different from ordinary techniques that require some form of sealing.

However, the pore sealing process, which is performed by electrodepositing a water-based paint inside the micropores and displacing water, has traditionally been problematic in terms of the durability of alumite products, and such paint When the composition was electrodeposited and anodized aluminum was sealed, the durability in corrosive environments used in tests such as the cast test, sulfite resistance test, and alkali resistance test was insufficient. The present inventor completed the present invention as a result of intensive research aimed at solving these defects.

That is, the present invention includes: A (a) a weakly basic monomer of 30 to 200 mol % based on (C) below, (b) a nonpolar monomer of 5 to 35 mol % of the total, and (C) an acid value of 30 to 35 mol %. 100 of the carboxyl group-containing monomer, (d) 5 to 15 mol% of the hydroxyl group-containing monomer based on the total, and (e) the remainder of the above (a) to (d) alkyl acrylate or (and) alkyl methacrylate. An acrylic resin component containing at least 5% by weight of an acrylic resin obtained by copolymerizing a polymerizable monomer that is an ester, and (B) whether 90% or more of the active hydrogens in the amino groups of the aminotriazine are alkoxymethylated. , or a part of the alkoxymethylation is methylenated at a ratio of 0.5 mole or less to aminotriazine, and 5% or less of the active hydrogen is methylolated, and the alkoxymethyl is The constituent alkoxy groups are 0.5 per aminotriazine skeleton.
A film-forming material composition comprising an aminotriazine compound in which ~3 are alkoxy groups having 2 to 4 carbon atoms and the remainder are methoxy groups is mixed with ammonia and ammonia substantially less than the number of carboxyl groups in the acrylic resin component. The present invention relates to a composition for electrodeposition of self-dispersing aluminum having an average particle diameter of at least 1000 A, which is neutralized with one or more amines and dispersed in water.

The reason why the average particle diameter of the aqueous dispersion used in the present invention is at least 1000A is because the permeation of corrosive gases, especially sulfur dioxide gas, which has the greatest effect on the corrosion of alumite products, is 1000A or more. This is based on the fact that it exhibits a special performance in that it exhibits a very significant reduction in coatings using an aqueous dispersion.
This effect was discovered for the first time by the present inventor. Because of this effect, the present invention uses an aqueous dispersion with an average particle size of 1000A or more.
Furthermore, when using the same composition, the cast test and alkali resistance test, which are substitute characteristics of alumite processed products, were 1000%
When an aqueous dispersion with an average particle size of A or more is used, an extremely excellent effect is shown, which is completely different from when an aqueous dispersion with an average particle size of 1000A or less is used. As described above, the present invention exhibits excellent effects regardless of whether or not the alumite is sealed. It is possible to obtain a highly corrosion-resistant alumite processed product without using special means of electrodepositing thermosetting paint inside the holes.

The performance exhibited by the present invention is achieved by the state and properties of the resin and dispersion used, and is disclosed in Japanese Patent Publication No. 41-14967 (Patent No. 517521).
Unlike , the resin cannot enter the pores of the alumite layer, but the performance is extremely excellent, especially when the hydration reaction is carried out in hot water or hot water at 50℃ or higher after anodizing the aluminum. ing. In the present invention, an acrylic resin having a weakly basic functional group and an acidic carboxyl group and a hydroxyl group in the same molecule and an acrylic resin containing a nonpolar monomer structure as an essential component and an aminotriazine compound as a crosslinking agent are used. By neutralizing the composition, which is a homogeneous mixture of the acrylic resin, with one or more of ammonia and/or amines in an amount substantially smaller than the carboxyl groups in the acrylic resin and dispersing the composition in water, Stable and strong water-dispersed particles are formed by forming a strong micelle structure or intraparticle salt between the functional group and the carboxyl group within and/or between molecules.

Furthermore, by using a non-polar monomer, the hydrophilicity of the water-dispersed particles is suppressed and affinity displacement with water in the alumite pores is prevented. In addition, by increasing the strength of the electrodeposited film by utilizing the bonding force between the basic functional group and the carboxyl group, volatilization of water in the alumite micropores is prevented, and the coating film is formed in the subsequent process. The baking process simultaneously performs a sufficient hydration reaction of the alumite and crosslinks the coating film. Weakly basic monomers used in the acrylic resin of the present invention include:
Acrylamide, N-alkyl substituted acrylamide (number of carbon atoms in alkyl: 4 or less), N-methylolacrylamide, N-alkoxymethylacrylamide, (appropriate number of carbon atoms in the alkoxy group is 1 to 5), and/or methacrylamide and methacrylamide At least one of the above derivatives is used.

The amount of the weakly basic monomer used must be at least 30 mol% of the carboxyl group-containing monomer blended into the resin. If the amount of the basic monomer is 30 mol % or less, the effects of the present invention cannot be obtained, as a matter of course.

Furthermore, the amount of the basic monomer should remain within 200 mole percent of the carboxyl group-containing monomer. 2
If the amount is more than 0.00 mol %, the stability of the water-dispersed particles is poor, and the particles settle during electrodeposition coating, making it difficult to perform a continuous and stable coating operation.

Furthermore, the nonpolar monomer used in the present invention refers to a monomer composed of carbon and hydrogen, and aromatic monomers such as styrene and vinyltoluene are particularly useful.

The use of such non-polar monomers is essential in the present invention, and the hydrophobicity of such monomers prevents the substitution of water and resin within the alumite micropores, and improves the smoothness and water resistance of the coating film after crosslinking by baking. Improve. In order to achieve such effects, it is essential that each monomer be present in an amount of 5 mol% or more of the total amount. However, the use of such hydrophobic monomers is preferably limited to 35 mol % or less in view of the flexibility and adhesion of the coating film. Further, as the carboxyl group-containing monomer, any monomer that can be copolymerized with other acrylic monomers can be used, but acrylic acid or methacrylic acid is preferable. The amount of these carboxy-containing monomers used is such that the acid value of the acrylic resin is 30.
It should be adjusted to indicate between 1 and 100.

If the acid value is less than 30, the water-dispersed particles of the paint tend to coagulate and settle, making it unstable and impractical; if it is more than 100, the coating efficiency during electrodeposition is poor and economical. Not. Furthermore, other acrylic monomers can be copolymerized to complete the acrylic resin of the present invention, but in order to complete the crosslinking with the aminotriazine compound and obtain a tough coating film, acrylic acid or methacrylic acid 2
It is essential to copolymerize a hydroxyl group-containing monomer such as -hydroxyethyl ester or hydroxypropyl ester in an amount of 5 to 15 mol%, preferably 8 to 11 mol% of the total monomers. When such hydroxyl group-containing monomers are not copolymerized, heat curing does not occur or is insufficient and swells in organic solvents, making it impossible to obtain sufficient strength. The remainder other than the above-mentioned monomers essential to the present invention is:
These are known polymerizable monomers conventionally used in this type of resin, ie, acrylic acid alkyl esters and/or methacrylic acid alkyl esters.

Acrylic acid amide and/or methacrylic acid amide and derivatives thereof are listed as the weak base functional group-containing monomer in the above-mentioned weak base functional group-containing and carboxyl group-containing acrylic resin that is essential in the present invention, but it is possible to use such monomers. This is an essential requirement of the present invention, and it is essential to use the carboxyl group-containing monomer within the above range.

Therefore, even if a strongly basic monomer such as N-N-dimethylamino methacrylate is used, the effects of the present invention cannot be obtained at all, and the present invention is not completed. As the aminotriazine compound used in the present invention, alkoxymethylated aminotriazine is useful.

More preferably, compounds are useful which, when dispersed alone in water, do not completely dissolve in water when added to at least one volume of water. In such an aminotriazine compound, 90% or more of the active hydrogen of the amino group of the aminotriazine is alkoxymethylated, or a part of the alkoxymethylation is 0.5% of the amino group of the aminotriazine.
It is methylenated in a proportion of less than mol, and 5% or less of the active hydrogen is methylolated, and the alkoxy group constituting the alkoxymethyl has 0.5 to 3 alkoxy groups per aminotriazine skeleton. Aminotriazine compounds having an alkoxy group having 2 to 4 carbon atoms and the remainder being a methoxy group are useful. Incidentally, methylenation as used herein means that aminotriazine forms a dimer, trimer or higher polymer through a methylene group. Such aminotriazine compounds do not have electrophoretic properties and do not electrodeposit when used alone in an aqueous dispersion system, and furthermore, they do not have the ability to form a coating film, and do not harden under normal coating film baking conditions. When such an aminotriazine compound is mixed with the acrylic resin and dispersed in water, uniform and stable water-dispersed particles are formed and electrodeposited. In the aminotriazine compound, when the alkoxymethyl group or the alkoxymethyl group and the methylene group account for less than 90% of the active hydrogen of the amino group, the aminotriazine compound is mixed with the acrylic resin or the aminotriazine compound during water dispersion. Condensation polymerization may occur, impairing the stability of the particles, or causing a significant change in the electrocoating conditions, making it impossible to work under stable coating conditions, or furthermore, causing a loss of smoothness on the electrocoated surface. It's inappropriate to play. Furthermore, when the methylene group exceeds 0.5 mole, the acrylic resin is stable. It cannot form water-dispersible particles and separates and settles from the acrylic resin. If the methylol group exceeds 5%, it will polycondense with the acrylic resin and/or the aminotriazine compound within the water-dispersed particles, affecting particle stability, electrodeposition coating conditions, coating surface smoothness, etc. It cannot be put to practical use until now. Furthermore, if the number of alkoxy groups having 2 to 4 carbon atoms among the alkoxy groups constituting the alkoxymethyl group is less than 0.5 per aminotriazine skeleton, the aminotriazine compound will dissolve in water of 1 or more. Since it is easily water-soluble, the aminotriazine compound separates from the dispersed particles and dissolves in water, resulting in poor transfer rate during electrodeposition and insufficient crosslinking during baking of the electrodeposition coating. The effects of the present invention cannot be fully exhibited. If the number exceeds three, uniform and stable particles with the acrylic resin cannot be obtained, and the aminotriazine compound separates from the particles and coagulates and settles. The excellent effects of the present invention are obtained by mixing the acrylic resin and the aminotriazine compound and adding ammonia and/or one or more amines in an amount substantially smaller than the number of carboxyl groups in the acrylic resin. and dispersed in water to obtain an average particle size of 100.
The best performance is obtained by making a dispersion liquid of 0A or more, dipping anodized aluminum if necessary in the dispersion liquid, electrodepositing it, and then hardening it by baking. If the amount of such acrylic resin is less than 5% by weight, there will be no effect even if a normal water-based acrylic resin that does not have weakly basic functional groups and only has carboxyl groups and hydroxyl groups is used in combination. As a result of further intensive research, it is essential that the acrylic resin contains the carboxyl group and hydroxyl group, but it is also essential that the acrylic resin has a number average molecular weight of 15,000 or more. However, when the basic-containing functional group acrylic resin and the acrylic resin are mixed, an acrylic resin having a non-polar monomer component of at least 5 mol % in the total acrylic resin is useful. Only when less than 5% by weight is used, the resulting alumite product exhibits almost the same effect as when such acrylic resin is not mixed.The reason why there is a limit to the use of such mixed acrylic resin is still unknown. However, a decrease in the amount of nonpolar monomer affects the hydrophobicity of the paint dispersion particles, and the molecular weight affects intraparticle micelle formation or intramolecular salt formation, and furthermore, when using an acrylic resin with a too low molecular weight, electrodeposition This is probably due to the deterioration of the strength of the deposited coating film.Furthermore, when the mixed acrylic resin was used in an amount of 5% or more, the characteristic effect of the acrylic resin containing weakly basic functional groups on the formation of water-dispersed particles suddenly increased. The mixing ratio of the acrylic resin component and the aminotriazine compound as a crosslinking agent is not particularly limited, but
Generally, a suitable weight ratio of acrylic resin component to aminotriazine compound is 80:20 to 40:60. 80:
When the acrylic resin component is more than 20:20, the degree of crosslinking of the baked coating film is insufficient and the hardness of the coating film is low, and when it is less than 40:60, the smoothness of the coated surface is impaired.

As the neutralizing agent used in the present invention, it is appropriate to use one or more of ammonia and/or amines. Examples of amines that can be used include alkylamines such as diethylamine, triethylamine, diisopropylamine, and trimethylamine, alkanolamines such as diethanolamine and triethanolamine, and alkanolamines such as dimethylaminoethanol.
Note that water-insoluble amines such as cyclohexylamine can also be used as auxiliary neutralizing agents if used in small amounts. The amount of neutralizing agent used in the coating composition should be in a molar ratio that is substantially less than the number of carboxyl groups present in the acrylic resin in the composition.

The term "substantially small number" cannot be defined uniformly because it varies depending on the carboxyl group concentration (acid value) in the acrylic resin, but for example, in the case of an acid value of 40, it is 80 to 95 with respect to carboxyl groups. mol%, 50 to 8 in case of acid value 70
5 mol% is suitable. If this number is exceeded, the average particle diameter of the water-dispersed particles will be less than 1000A, or the particles will become water-soluble and the effects of the present invention cannot be exhibited. If less than this,
Water-dispersed particles become unstable. The essential composition in the present invention is as described above, but in order to stabilize the water-dispersed particles,
Additionally, hydrophilic organic solvents may be used to reduce viscosity during paint handling.

Examples of organic solvents that can be used include alcohols having 4 or less carbon atoms, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol, Sec-butyl alcohol, IsO-butyl alcohol, and n-butyl alcohol. , ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. One or more monoethers of ethylene glycol and an alcohol having 4 or less carbon atoms can be used. When using these organic solvents, it is essential to use them within a range that does not cause the dispersed particles to be dispersed.
That is, in the composition of the present invention, alcohols having 3 or less carbon atoms and t-butyl alcohol can be used in any ratio, but ethylene glycol monoethers can be used in combination with the acrylic resin component in the coating composition. It is preferable to use 3 parts by weight or less per 10 parts by weight of the triazine compound. If it is more than this, the average particle diameter of the water-dispersed particles becomes 1000A or less, and the effects of the present invention cannot be exhibited. Furthermore, in the present invention, water-soluble oxyacid salts such as sodium silicate, potassium silicate, potassium molybutate, ammonium molybutate, potassium borate, and ammonium stannate may be added to the acrylic resin in the coating composition, unless there is a particular problem. It can be used in a proportion of 1 part by weight or less per 10 parts by weight of the component and the aminotriazine compound.

By using such a water-soluble oxyacid salt, an insoluble metal salt is formed on the alumite surface layer with metal ions such as aluminum eluted from the alumite micropores during electrodeposition,
Prevents deterioration of painted surface smoothness due to penetration of metal ions into the paint film. The self-dispersing coating composition of the present invention is
A homogeneous mixture of an acrylic resin and an aminotriazine compound, which is a coating film-forming material, is mixed with ammonia or amines that migrate to the opposite electrode during electrodeposition, and the carboxyl groups in the film-forming material are neutralized and ionized to form water-dispersed particles. Compositions such as ordinary aqueous emulsions in which water-dispersed particles are stabilized with a low-molecular surfactant do not exhibit the effects of the present invention at all. By using the self-emulsifying water-dispersed paint having the composition of the present invention, it can be applied in the same way as the electrodeposition coating of other conductive materials without electrodeposition in the fine pores of alumite, resulting in excellent alumite processing. can manufacture products.

In the electrodeposition coating method using the composition of the present invention, in addition to aluminum that is not subjected to anodizing treatment, aluminum that has been subjected to a known anodizing treatment is sufficiently washed with water to remove the treatment liquid adhering to the surface, and then The product is completed by drying most of the washing water adhering to the ζ, then painting it according to the usual electrodeposition coating method, and finally curing it by heating. Preferably, the anodized aluminum is thoroughly washed with water. After that, place it in warm or hot water of 50°C or higher for at least 3 hours.
Dip for a minute and paint a part of the alumite surface onto the boehmite material.

More preferably, the anodized aluminum is immersed in an acidic sulfuric acid solution containing nickel sulfate as a main component, and subjected to alternating current electrolysis to deposit the metal containing nickel as a main component into the micropores of the anodized film. When alumite is electrodeposited, the metal is ionized and eluted out of the fine pores of the alumite, and a hot water treatment should be performed to seal the pores to the extent that the colored alumite does not discolor. Such conditions are at least
Hot water treatment conditions of 5 minutes or more at 50°C are required. Such hydrothermal treatment may be carried out with deionized water or even with 90%
If the temperature is above 0.degree. C., it is preferable to treat with an aqueous solution containing a trace amount of a water-soluble metal salt such as nickel acetate, cobalt acetate, nickel sulfate, sodium salt of phosphoric acid, or sodium silicate. By performing such treatment, an alumite processed product having even better durability can be obtained. After such treatment, it may be further washed with water, but before the treated material is immersed in the electrodeposition coating liquid, it should be left until most of the water adhering to the surface of the treated material has dried. Electrodeposition painting should then be carried out. By taking such measures,
Contamination of the electrodeposited solution can be minimized, and pinholes and deterioration in smoothness of the electrodeposited surface caused by this can be prevented. When carrying out electrodeposition coating using the composition of the present invention, the concentration of the electrodeposition coating liquid is suitably 4% to 15%. If it is less than 4%, the coating voltage becomes too high, and if it is more than 15%, the loss of the coating liquid to the outside of the system is large, and neither is economical.

This composition can be recovered by known ultrafiltration or reverse osmosis filtration. Although it is possible, if the amount taken out of the system is large, the recovery cost will be high and it is not economically advantageous. Further, the appropriate electrodeposition coating temperature is in the range of 15°C to 35°C. Although it is possible to coat at temperatures below 15°C, it is not industrially advisable because the voltage becomes high, making it difficult to obtain a high film thickness, and furthermore, the cooling cost for temperature control increases.

If the electrodeposition solution temperature is 35° C. or higher, the electrodeposition coating composition is likely to undergo deterioration, and when used for a long period of time, the coating solution must be recycled, which is not advantageous. The coating voltage of this coating composition can be used between 80V and 350V. Furthermore, a major feature of the electrodeposition coating of the composition according to the present invention is that even if the same composition is electrodeposited and then washed with water to remove the non-electrodeposited coating liquid adhering to the surface and then baked and cured, the coating Even if the solution is baked and hardened without washing with water, that is, without washing with water, it is possible to obtain an excellent aluminum product with no change in appearance or performance.

Such special properties are a surprising fact and are effects that have never been achieved with other electrodeposition coating compositions. The reason for this effect is probably that a weakly basic functional group and a weakly acidic carboxyl group exist in the same molecule in an appropriate ratio. In fact, in a composition in which weakly basic functional groups are excluded from the present composition, when waterless electrodeposition coating is performed, uneven gloss will occur on the surface of the alumite processed product, resulting in a worthless finish. When washing with water is performed after electrodeposition coating using the coating composition of the present invention, loss of the coating material from the electrodeposition coating tank can be prevented using a known method using ultrafiltration or reverse osmosis filtration equipment. It can be recovered. Furthermore, in order to carry out electrodeposition coating and cure the coating film deposited on the anodic oxide film, it is preferable to heat and cure the coated object at a temperature of 170°C to 200°C for one to five times.170 If the temperature is below ℃, crosslinking will be insufficient and sufficient coating hardness will not be obtained, and if the temperature is above 200℃, the aluminum to be coated will undergo an annealing phenomenon and the strength of the processed product will decrease. Undesirable.

The composition of the present invention can be electrodeposited inside the fine pores of alumite by applying a normal electrodeposition coating method, whether immediately after anodization or on an anodized film treated with hot water. However, it shows excellent adhesion and excellent durability.

Furthermore, when carrying out electrodeposition coating, the undeposited paint liquid that adheres to the deposited paint film may be removed by washing with water, or even if it is heated and cured without washing without removing it, there will be no difference. Has excellent painted appearance and performance. Examples will be described in more detail below.

In the examples, parts indicate parts by weight. Example 1 w parts styrene, 8 parts acrylamide, w parts acrylic acid,
Methyl methacrylate part, 2-hydroxyethyl methacrylate part, ethyl acrylate 40 parts, azobisisobutyronitrile 0.8 part, and isopropyl alcohol 5 parts
0 part was charged into a reaction vessel and polymerized in a boiling state for 2 hours.

The acid value of the obtained acrylic resin is 77, and the molecular weight is approximately 310.
It was 00. Add 150 parts of this resin solution to
40 (manufactured by Sanwa Chemical Co., Ltd., partially butoxylated methylaminotriazine; butoxy amount 1.0 to 1.5 mol/triazine) (1) part was added, stirred uniformly, and then 9.7 parts of triethylamine (in acrylic resin) was added. (0.7 mol based on the carboxyl group), deionized water was added so that the solid content of the coating material was 10%, and the mixture was stirred and dispersed. The particle size of this dispersion was 1000 to 7000A. The following aluminum material was electrodeposited using this paint bath in a conventional manner, and the results are as follows. Experiment A Aluminum alloy (6068
S) was immersed in a 15% sulfuric acid solution at a temperature of 20°C and a current density of 1A.
After anodizing under the conditions of Idd, the sample was thoroughly rinsed with water at room temperature, and the surface water was removed at room temperature until the surface was almost dry.

The thickness of the alumite film obtained was 8μ. After electrodeposition coating was performed using this material, it was washed with water and cured by heating at 185° C. for 3 cycles. The resulting coating film thickness was 9μ. Experiment B: The same aluminum alloy as in Experiment A was used and anodized using the same method, washed with water, treated with hot water at 80°C, and then left indoors to remove water adhering to the surface. Electrodeposition coating was performed in the same manner as in Experiment A, and the coating was heated and cured.

Both the alumite film thickness and the coating film thickness were the same as in Experiment A.
Experiment C: Using the same aluminum alloy as in Experiment A, it was anodized in the same manner, washed with water, and anodized with 30 ppm sodium silicate solution.
After treatment with hot water at 5° C. for 15 minutes, it was washed with water, and then left indoors to remove water adhering to the surface. After that, it was electrodeposited in the same manner as in Experiment A, and then cured by heating.

Both the alumite film thickness and the coating film thickness were the same as in Experiment A.
The following table shows the coated surface condition, durability, and adhesion of the coated plates obtained in the above experiments. Example 2 15 parts of styrene, N-butoxymethylacrylamide m
part, methacrylic acid part, methyl methacrylate part, 2-ethylhexyl methacrylate 5 parts, 2-hydroxyethyl acrylate part w, isobutyl acrylate 3(2), azobisisobutyronitrile 0.5 part, isopropyl 50 parts of alcohol and m parts of ethylene glycol monobutyl ether were placed in a reaction vessel and copolymerized at the boiling point for a period of time.

The resulting resin had a molecular weight of 4,100 and an acid value of 76. (This varnish is called varnish A.) On the other hand, styrene w
parts, 2-hydroxyethyl methacrylate w parts, acrylic acid w parts, methyl methacrylate (to) parts, methacrylic acid 2 parts
- 10 parts of ethylhexyl, (up to) parts of methyl acrylate,
1.0 part of benzoyl peroxide and 4 parts of isopropyl alcohol were charged into a reaction vessel, and at the boiling point 2CB!
Copolymerization was carried out between f.

The resulting resin had a molecular weight of 230,000 and an acid value of 79. (This varnish is called varnish B.) The varnish A1 mark part and the varnish BlW part (varnish A is 55% of the total acrylic resin.
weight%), Cymel NO. lll6 (manufactured by American Cyanamid, partially ethoxylated methylaminotriazine; ethoxy amount, 2.0 to 2.5 mo/triazine) 103 parts,
After thoroughly mixing 12.7 parts of dimethylaminoethanol (0.6 equivalents relative to the carboxyl group of the gold acrylic resin), deionized water was added to prepare an electrodeposition coating bath having a solids content of 12%.

The coating bath was a white dispersion with particle sizes ranging from 1000A to 4000A. Using this coating bath, coating experiments were carried out on three types of alumite materials as in Example 1, and the results were as follows. 8 Example 3 Adding 1% water-dispersible red dye to the composition of Example 1,
A red electrodeposition bath was created.

After etching the aluminum plate with a 5% caustic soda aqueous solution, it was washed with water and further soaked in boiling deionized water for 3 minutes.
A boehmite-treated plate without micropores was created by powder treatment.

Furthermore, Experiment A of Example 1, . B. ．． Electrodeposition coating was performed using the treated material used in step C and the boehmite treated plate, and the coating was heated and cured. In all cases, good red coating films were obtained. Further, this coating film was removed with a release agent to form a boehmite film and Experiment A. B. ．． As a result of observing changes in the surface of the film of treated material C using a microscope, there was no difference in the color change on the film of these materials, and electrodeposition on porous alumite by this composition was superior to that of other non-porous alumite. It was found that there is no difference between this method and the electrodeposition coating of metal objects. Example 4 In the varnish A1 (1) part of Example 2, 45 parts of the crosslinking agent "Nipure Lac MX-40", 0.07 parts of ammonium molybutate, and 8.3 parts of triethylamine (carboxyl group in the acrylic resin) were added. 0.6 mol) was added thereto, and deionized water was added so that the solid content of the paint was 7%, and the mixture was stirred and dispersed.

The particle size of this dispersion was 2000A to 4000A. On the other hand, aluminum alloy (6063S) was anodized in a 15% sulfuric acid solution according to a conventional method, washed with water, and then
After hot water treatment in deionized water at 0° C. for 2 minutes, surface water was removed and electrodeposition was performed in the above coating bath.

After electrodeposition, Experiment A was washed with water and then heated and cured at 190°C, while Experiment B was left indoors for 3 minutes without being washed with water and immediately heated and cured. The heat curing conditions were the same as in Experiment A. Alumite film thickness 10μ, coating film thickness 12
μ was hot. The results were as follows.

Comparative Example 1 2 parts of vinyltoluene, 30 parts of methyl methacrylate, methyl acrylate, 25 parts of ethyl acrylate, 5 parts of 2-hydroxyethyl methacrylate, 13 parts of 2-hydroxyethyl acrylate, 6 parts of methacrylic acid, isopropyl Part (a) of alcohol, part ethylene glycol monoethyl ether, and 1 part benzoyl peroxide were charged and reacted for one hour at boiling temperature to synthesize an acrylic resin varnish.

This acrylic resin had an acid value of 51 and a molecular weight of 23,000. Add 1 (4) parts of a water-soluble aminotriazine compound (Cymel NO.3Ol: American Cyanamid Company, hexakismethoxymethylaminotriazine) to the above varnish 15 (2), and further add 9 parts of triethylamine to make the solid content 10%. Deionized water was added and stirred to prepare an electrodeposition coating bath.

This bath was in the form of a slightly cloudy solution and had an average particle diameter of less than 1000 A, which was unmeasurable. Using this bath, an experiment was carried out in the same manner as in Example 1, and the results were as follows. Comparative Example 2 3 parts of styrene, 55 parts of methyl methacrylate, 5 parts of 2-ethylhexyl methacrylate, 5 parts of acrylic acid, w parts of 2-hydroxyethyl methacrylate, ethyl acrylate, 50 parts of isopropyl alcohol, and azobis After 0.6 parts of isobutyronitrile was charged into a reaction vessel and copolymerized for 1 hour, w parts of ethylene glycol monobutyl ether and 6(2) of isopropyl alcohol were further added to prepare an acrylic resin varnish.

This acrylic resin had a molecular weight of 3,700 and an acid value of 36. Cymel NO. 220 parts of this acrylic varnish. 3
One part of Ol and 7y of triethylamine were added, mixed well, and diluted with deionized water to a solids content of 12%.

This coating liquid was completely water-soluble. In Comparative Example 1, after anodizing, the coating was performed in an air-dried state after washing with water or further hot water treatment, so there was a risk that the paint would not be electrodeposited within the fine pores of the alumite. Now, the following experiment was conducted using the above paint bath. Experiment A1 After anodic oxidation under the same conditions as in Experiment A of Example 1, electrodeposition coating was immediately applied, and after washing with water, it was cured by heating at 185° C. with three powders.

Experiment B1 After anodizing under the same conditions as Experiment A of Example 1, it was washed with water, immersed in an electrodeposition coating liquid while still wet, immediately applied with electrodeposition coating, and after washing with water, heated and cured with 3 powders at 185°C. I forced it.

The results were as shown in the table below. As shown in the table above, it is impossible to even obtain a continuous coating when electrodeposited immediately after anodizing, so after anodizing, wash with water and apply electrodeposition immediately with a water layer on the surface. In Experiment B, the coated surface also yellowed and uneven gloss appeared, which was thought to be due to uneven electrodeposition, and the product was worthless as an alumite processed product.

In addition, in this comparative example, the same experiment was performed with the electrodeposition coating solution subjected to anion exchange and then cation exchange to remove harmful ions during electrodeposition in the electrodeposition coating solution, but the results were It was the same as before ion exchange. Comparative Example 3 In Comparative Example 2, unexpectedly bad results were obtained, so we created a coating composition that was thought to be more electrodeposited into micropores by keeping the molecular weight of the acrylic resin in the coating composition low. did.

That is, in the formulation of the acrylic resin varnish of Comparative Example 2, the amount of azobisisobutyronitrile was increased to 3 parts,
Acrylic resin varnish was synthesized with the other formulations being exactly the same.

The molecular weight of the acrylic resin was 9,000. A paint bath was prepared using this acrylic resin and having the same formulation as in Comparative Example 2.
The coating liquid was completely water soluble. Using this coating bath, an aluminum treated material prepared under the same conditions as in Comparative Example 2 was electrodeposited, washed with water, and cured by heating. The results were as shown in the table below. In the above three comparative examples, test results were shown using coating compositions not according to the present invention, but the coating compositions of comparative examples 1 and 2 are the coating compositions most commonly used for aluminum electrodeposition at present. It is a thing.

Furthermore, in accordance with the teachings of known technology, in order to ensure thorough electrodeposition into the fine pores of alumite, a coating composition with a molecular weight 11 degrees lower than that of ordinary alumite electrodeposition was prepared and its effects were investigated. No appreciable results were obtained. Due to the excellent effects of the coating composition, the present invention can be used not only without anodizing treatment, but also with sufficient water washing and removal of washing water after anodizing, or with hot water treatment after washing with water. After this process, the water on the anodic oxide film is removed and the material is electrodeposited and then washed with water or heat-cured without washing, resulting in an aluminum processed material with excellent performance.

Claims (1)

[Claims] 1 A (a) 30 to 200 mol% of a weakly basic monomer based on (c) below, (b) a nonpolar monomer of 5 to 35 mol% of the total, (c) an amount that gives an acid value of 30 to 100 (d) 5 to 15 mol% of the total hydroxyl group-containing monomer, and (e) the above (a) to (d)
) an acrylic resin component containing at least 50% by weight of an acrylic resin obtained by copolymerizing the remaining acrylic acid alkyl ester or (and) methacrylic acid alkyl ester polymerizable monomer; 90% or more of the active hydrogen is alkoxymethylated, or a part of the alkoxymethylation is methylenated at a ratio of 0.5 mol or less to aminotriazine, and 5% or less of the active hydrogen is methylol. An aminotriazine compound in which 0.5 to 3 alkoxy groups constituting the alkoxymethyl are alkoxy groups having 2 to 4 carbon atoms per aminotriazine skeleton, and the rest are methoxy groups. An average particle diameter of at least 1000 Å obtained by neutralizing a film-forming material composition consisting of A self-dispersing aluminum electrodeposition coating composition comprising: